Waste streams are a growing concern to the environment. Authorities impose increasingly stringent requirement as to the disposal of waste streams. In refineries waste sludges are obtained during the work up of crude oil fractions. Such sludges may include water, salt, catalyst wastes, dirt like sand, and heavy oil. Sludges like these are not allowed to be disposed of without pre-treatment.
A suitable pre-treatment could comprise a filtration to separate the solids from the liquids. Problems that could arise in connection with filtration relate to filtration rates, moisture content of the filter cake obtained and leachability of metal ions from the filter cake. The problem of filtration rate can be encountered by the use of filter aids. In the industry the use of diatomaceous earth as filter aid is well-known. A way to solve the leachability problems resides in the fixation of the metals in cement. Thereto the waste may be mixed with cement and the admixture may be allowed to set and a solid hard material is obtained which passes the leachability requirements set by the authorities. Another way to solve the problem of the metal ions is to incorporate the metal ions into the cement. Hence, it has been proposed to use solid material resulting from the filtration of waste as fuel in cement kilns so that the metal ions contained in such material would be retained in the cement produced in the kiln. Cement producers, however, set certain requirements as to the quality of the material to be used as fuel. One such requirement is that the heating value of the material is at least 5,000 Btu/lb (1 Btu/lb equals 2.32444 J/g). Another requirement is that the moisture content in the material does not exceed 10% wt, based on the total material. A third requirement is that the material is non-sticking to enable pneumatic transportation.
It is evident that the use of diatomaceous earth as filter aid only aids in solving any filtration problems. It does not contribute to the heating value of the eventual material that may be used as fuel.
It is an object of the present invention to provide a process in which both filtration rate is improved and the resulting material has a high heating value, so that it can be used as fuel.
It is another object of the invention to provide for a fuel that can be used in a cement kiln and fulfills the requirements set by the cement manufacturers.
It is a further object of the invention to provide for a process of producing cement using a fuel obtained from waste sludges.
Another object of the invention is to produce non-sticking dried material from refinery waste sludge as solid fuel for a cement kiln which material has satisfactory moisture and oil content and an acceptable heating value.